(1) Field of the Invention
The present invention relates generally to separators for separating processed material from a grinding medium in a dispersing and grinding apparatus and more particularly, to a separator having dispersing means for centrifugally dispersing the grinding medium which tends to accumulate at the region where the separated processed material exits from the apparatus.
(2) Background Information
Dispersing and grinding apparatus are in widespread use for dispersing, grinding and agitating various types of materials. These apparatus are commonly known as dispersion agitators or grinding mills and utilize a grinding medium, such as balls, beads or other particulates to accomplish the grinding and comminuting action. After the material is suitably dispersed, ground and agitated, the processed material must be separated from the grinding medium. For this purpose, a separator is frequently installed at the discharge end of the apparatus for separating the processed material from the grinding medium such that the processed material is discharged from the apparatus while the grinding medium is retained in the apparatus for re-use.
One common type of separator is the so-called dynamic separator which comprises a stationary stator and a rotatable rotor. The stator and rotor are spaced apart a slight distance so that a small gap exists between the rims of the rotor and the stator to define a discharge passage for the processed material. The size of the gap is smaller than the size of the particulates which constitute the grinding medium thereby ensuring that the grinding medium cannot pass through the gap.
One drawback of such separators is that the stator, the rotor, or both, become quickly abraded by the grinding medium and, therefore, need frequent replacement. This is due to the fact that the grinding medium tends to accumulate and concentrate at the rim area of the rotor so that as the rotor rotates, the grinding medium abrades and wears out the confronting surfaces of the stator and rotor. Various attempts have been made to solve this problem though none has proved successful. For example, it has been proposed to configure the rotor in an elliptical shape to reduce the concentration of the grinding medium at the rim area of the rotor. It has also been proposed to mount the rotor eccentrically relative to the stator so that as the rotor rotates, the relative positions of the rim areas of the rotor and the stator constantly change so as to avoid the concentration of the grinding medium at the rim area of the rotor. These prior art attempts are disclosed, for example, in U.S. Pat. No. 4,534,516. However, these prior art separators do not prevent rapid wearing out of the rotor because the periphery of the rotor itself is used to push the grinding medium outwardly. Hence, the rotor rapidly becomes worn and requires frequent replacement. Moreover, when it becomes necessary to replace the rotor in the prior art separators, it is usually necessary to remove and replace the entire rotor assembly, and such a task is both troublesome and uneconomical.